Electroplating cell



May 23, 1944. T. J. KEA'IY'ING 2,349,662

. vELECTROPLATING CELL Filed Jan. 8, 1941 2 Sheets-Sheet 1 flrsulal/'orzWITNEssEs; 2

May 23, i944. T. J. KEATING yELEC'1.R(`)PI.|A'1ING CELL Filed Jan. s,19'41 2 Sheets-Sheet 2 INVENTOR i d gy. w a, A z 5 4 fn .a 4 4 U4 J. @uvf q wmf Il a Y lllll E f A m f 4 0. my. f,

Patented May 23, 1944 ELECTROPLATING CELL Thomas J. Keating, Bloomfield,N. J., assigner to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a corporation of Pennsylvania Application. January 8,1941, Serial No. 373,545 s claims (o1. .2M- 252) This invention relatesto electroplating baths, and more particularly, to sludge retainers foruse in connection with anodes.

In order to provide for bright and clean electroplating work, it isrequired that the bath be `free from colloidal suspensions and othermestruction of the fabric lbags and necessitated their frequentreplacement.

The object of this invention is to provide for a durable metallic sludgeretainer for anodes.

Other objects of the invention will be obvious and will, in part, appearhereinafter as disclosed by the specification and drawings.

Reference should be made to the accompany ing drawings, in which:

Figure 1 is a top plan view of the general assembly of an electroplatingbath;

Fig. 2 is a section on lines Il-II of Fig. 1;

Fig. 3 is a section on lines III-III of Fig. l;

Fig. 4 is a section taken along lines IV--IV of Fig. 3;

Fig. 5 is a section taken along lines V--V of Fig. 3; and

Fig. 6 is a partial section taken along lines VI-VI of Fig. 5.

It has been found that by localizing any sludges and solids present inthe electrolyte about anodes which are prone to sludge during operationof an electroplating bath, the detrimental eiect of the sludge issubstantially elimlnated. In particular, the placing about the anodes ofa screen having a sufficiently fine mesh will ensure that all of thesludge deposited by the anodes will be retained and prevented fromcontaminating the work being electroplated.

It has been found that sludge retainers made of fine metal screen orfabric have qualities which make them especially desirable forlocalizing the sludge about the anode. The necessary fundamentalproperties of the metal ernbodied in the screens are that the metal beinert in the electrolyte used for the electroplating bath. Furthermore,due to the fact that the surface of the electrolyte is in contact withoxygen and other gases of the atmosphere, which may cause increasedchemical activity, the metal inthe sludge retainer therefore should havecharacteristics which render it also inert to the more active surfaceportions of the bath.

It is well known that anode covers of ordinary cellulcsic materialsfrequently fail at a point a short distance above the surface of theelectrolyte by reason of the evaporation of the electrolyte carriedabove the surface on the material by capillary action. Highly corrosivecrystals of chemicals result from this evaporation. Accordingly it is afurther required qualification for the metal used in the retainer thatit be unharmed by crystals of chemicals resulting from evaporation ofthe electrolyte.

From the operating standpoint of an electroplating bath. it is desirablethat sludge retainers be both easily applied to the electroplating bathabout the anodes and be readily removable. In many instances, it isparticularly desirable that the sludge retainer not interfere with theremoval and addition of anodes as the anodes are plated out or changed,The prior art sludge bags had to be tied and untied by hand about eachanode.

A commercially satisfactory sludge retainer should be so constructedthat it can be easily cleaned of the sludge deposit present thereinwithout the use of any special tools or equipment.

A further requirement is that the retainer should not waste any currentor interfere with the plating operation.

The sludge retainer described herein and shown in the several gures ofthe drawings meets the various requirements listed hereinabove.

yThe metal which is suitable for use in any plating bath depends on thechemicals present by Various electrolytes is well known in the art andno extensive list of the metals suitable for results.

the various electrolytes is given other than those above.

Referring to Figure 1 of the drawings, an electroplating tank Il]including eight sludge retainers is shown. The electroplating tankconsists of a large receptacle I2 composed of a treated wood body withan internal lining of lead or other resisting metal. Anode conductorbars I4 are disposed on either side of the cathode conductor bar I6 onwhich the articles to be plated are hung. The anode bars I4 support, aplurality of anode hangers I8 which carry the anodes 20. The eightsludge retainers 22 hang from the anode bars by means of hooked supports24. Insulating pads 25 prevent current flow into the sludge retainers 22from conductor bars I4.

Referring to Figs. 2 and 3 of the drawings, there are shown the frontand back views, respectively, of a sludge retainer 22. The sludgeretainer consists of a bottom sludge pan 26 which is substantiallyimperforate. Attached to the upper edges of the pan 26 is a main frontscreen 30 which extends about both ends and the side of the retainerwhich is directed toward the object being plated. A second back screen36 is attached to the side of the pan remote from the cathode. As showninthe drawings, the screens do not extend up to the` surface of theelectrolyte but terminate a short distance below the surface. Asubstantially imperforate rim member is attached to the upwardextremities of the two screens and extends above the surface of theelectrolyte. It is believed that an imperforate rim memberv 42 havingconsiderable thickness would be somewhat more resistant to theintensified strength -of the electrolyte at the surface than would a 'newire mesh screen. The hooked suspension members 24 for the retainer arepreferably attached to the pan 26 and the upper rim member 42.

Referring to Fig. of the drawings, a more detailed view of theconstruction and related parts of the sludge retainer 22 is shown. Thepan member 26 includes a double thickness rim 28 produced by foldingover its edges. This double thickness rim is provided with tapped holes29 for the purpose of supporting the wire mesh screens.

Ihe wire mesh screens 30 and 36 have been made of 180 mesh 18-8stainless steel for use in'zinc cyanide plating solutions withsatisfactory Screens woven to this fine mesh have been found to besuflicient to function by themselves to substantially prevent passage ofsludge.

VThe screen 36 is placed within a framework 32 which consists of aformed U-shaped member clamped about theedges of the screen. Retainingmachine screws 34 passing through the frame member 32 engage in thetapped holes 29 in the .rim 28 of the pan. The rear screen member 36 isalso supported by means of a rectangular U- shaped frame 38. Machinescrews 40 provide for the attachment of screen 36 to the pan.

A suitable construction for the upper rim member which is partly withinthe electrolyte and partly exposed to the atmosphere, is best shown inFig. 5. The rim member consists of a continuous strip of metal 42, thelower edge of which is doubled over in order to provide a rim 44 withtapped holes 45 for receiving screen retaining machine screws 34 and 40.A channel 46 is welded or otherwise attached to the upper edgev of therim member 42 for reenforcement. In addition, as shown in Fig. 6, thefront corners of the rim member 42 are reenforced with round bars 48,

while the rear corners of the rim member are reenforced with square bars50.

The suspension members 24 are attached by means of welding to the upperrim member 42 and the pan member 26. Other means of attaching thesuspension members 24 to the sludge retainer body may be employed. Theinsulating pads 25 prevent :How of current through the retainer. 'I'heoperating efficiency of the plating unit will be decreased if current ispermitted to pass through the body of the retainer 22. The insulatingpads 25 may be of rubber, phenolic resins or other suitable dielectricmaterials. While the insulators 25 are shown as attached to anode barsI4, they may be attached to, or made part of, the support 24, thusrequiring no care in suspending the sludge retainer on the anodeconductor bar. All or part of the support 24 may be made of a dielectricmaterial. It would be feasible, in some instances, to provide insulatedsupports separate from the anode conductor for suspension of the sludgeretainer 22, thus rendering the insulator pads 25 unnecessary.

The rear screen 36, with its reenforcing frame 38, is readily removablefrom the retainer by removing the several machine screws 46. Only a fewmachine screws 40 are necessary for properly supporting the screen 36and its removal is a simple operation. Due t0 thefact that the sludgeretainer is a deep and narrow basket, the problem of removing sludgetherefrom is greatly simplified by providing the removable back screen36.

The sludge retainer 22 may be taken out of the electroplating bath atany time that the sludge accumulation therein has reached the extentthat the bottom pan 26 is nearly full. The anode bars 20 are removed rstfrom the bath, then the workman simply grasps the suspension members 24and lifts out the retainer slowly from the electrolyte to permit theelectrolyte to flow out. It is advisable to tilt the retainer slightlyin order to ensure that most of the electrolyte runs out of the pan.After the retainer has been removed from the bath, the back screen 36 istaken 01T by removing the machine screws 40. A small shovel or any otherconvenient implement may be readily inserted into the pan and the sludgedeposit taken out. Thereafter a water hose or other fluid line may beemployed to clean out the screen and wash out the pan. By replacing theback screen 36, the sludge retainer is vready for use again.

It will be appreciated that the sludge retainer disclosed by theinstantl invention will last indefinitely in electrolytes which do notreact with the metal employed for making the retainer. By using the samemetal for both screen, pan and upper rim member, no local electrolyticcorrosion can take place. The retainer should last vindefinitely ascompared to the customary cotton or other fabric sludge retainers. Thepan is of a rigid and strong construction which will support fallenanodes, a great accumulation of sludge, and anode fragments. Therelatively large amount of open area for the passage of the metallicions fa;- cilitates electroplating. It is a simple and convenient matterto suspend the container from the,

anode bars on the anode hangers.

The retainer is more convenient than the conventional sludge retainerinasmuch as the conventional sludge retainers generally enclose a singleanode. The present retainer is designed for cooperation with a pluralityof anode bars. Therefore, less work is necessary to clean the sludgeretainers in the present case than would be required with the greaternumber of sludge retainers required heretofore with the same number ofanodes.

Although one form of the invention is shown and described herein, itwill be understood that other changes may be made without departing fromthe spirit of the invention or the scope of the following claims.

I claim as my invention:

1. In an electrolytic cell including an electrolyte, anode supports, andan anode suspended in the electrolyte, the anode depositing a sludgeduring operation of the cell, a metallic retainer surrounding the anodefor catching the sludge comprising, in combination, a pan below theanode, a rim member about the anode extending through the surface of theelectrolyte, suspension means electrically insulated from the anodesupports for supporting the pan and rim from the anode supports, and ane metallic screen attached to the edges of the pan and extendingupwardly and attached to the portion of the rim member below the surfaceof the electrolyte, the metallic screen being of a nneness suillcient tofunction by itself to substantially prevent the passage of sludgetherethrough, the pan, rim member, suspension means, and the screenbeing composed of metal inert to the electrolyte.

2. In an electrolytic plating cell including an electrolyte, anodesupports, and an anode suspended from the anode supports in theelectrolyte, the anode depositing a sludge during operation of the cell,a metallic retainer surrounding the anode for catching the sludgecomprising, in combination, a pan below the anode, a, rim member aboutthe anode extending through the surface of the electrolyte, suspensionmeans electrically insulated from the anode supports attached to the panand rim member for supporting the retainer from the anode supports, anda metallic screen attached to the edges of the pan and extendingupwardly and attached to the portion of the rim member below the surfaceof the electrolyte, the metallic screen including a panel portionremovably attached to the pan to provide for removal of sludge depositedin the pan, the metallic screen being of a ineness sufficient tofunction by itself to substantially prevent passage therethrough of thesludge, the pan, the rim member, suspension means, and the screen beingcomposed of a metal insert to the electrolyte.

3. In an electroplating apparatus comprising an electrolytic bath, acathode and an anode for making deposits on the cathode, the dissolutionof the anode causing a sludge about the anode, a metallic sludgeretainer associated with the anode for collecting the sludge, theretainer comprising a metallic screen of suicient flneness to functionby itself to substantially prevent the passage of sludge therethrough,the screen having essentially vertical walls, an imperforate metallicpan for collecting sludge disposed below the anode in cooperativerelation with the screen and the sides of the pan being fitted to thescreen to form an extension thereof to provide an enclosure to preventsludge from escaping into the electrolyte outside the retainer andsupporting means for the pan and screen for suspending them in theelectrolyte, the supporting means including electrically insulatingportions to prevent electrical current from passing to the retainer, themetallic retainer being composed of a metal substantially inert to theelectrolyte.

THOMAS J. KEATING.

